The Effects of Microstructure on the Brightness of Pulsed Laser Deposited Y 2 O 3 :Eu Thin Film Phosphors for Field Emis
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e Effects of Microstructure on the Brightness of Pulsed Laser Deposited Y2O3:Eu Thin Film Phosphors for Field Emission Displays K. G. Cho, R. K. Singh, D. Kumar, P. H. Holloway, H-J. Gao1, S. J. Pennycook1, G. Russell2, and B. K. Wagner2 Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611. 1 Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6030. 2 PTCOE, Georgia Institute of Technology, Manufacturing Research Center, Atlanta, GA 30332. ABSTRACT In order to investigate the effect of microstructure on the brightness of thin film phosphors for field emission displays, Y2O3:Eu thin film phosphors were prepared using pulsed laser deposition. To deconvolute the effects experimentally, the Y2O3:Eu films of controlled thickness and microstructure were prepared on various substrate materials such as amorphous quartz, (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon wafers. Cathodoluminescent brightness and efficiency of the films were obtained in both transmission and reflection modes. The Y2O3:Eu films deposited on the quartz substrates showed the maximum brightness followed by the films on (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon substrates. The role of interface scattering of the emitted light on the film brightness will be discussed together with changing surface roughness and film thickness. INTRODUCTION There has been significant interest in the development of thin film phosphors (TFPs) for field emission displays (FEDs). Since the field emitter tips are in close proximity to the phosphor screen in FEDs, there exist two major concerns using powder phosphors in terms of debonding and outgassing. Any failure of adhesion may cause debonding of powder particles from the bulk phosphor screen. The free particles debonded from bulk powder layer will block the gates of the field emitter tips. This blocking of emitter tips will eventually cause no light output from certain area of screen. Outgassing is another major concern of powder phosphors. The residual gases outcoming from the binding materials for powder particles and the relatively porous structure of powder layer itself will increase the gas pressure of the vacuum sealed device under energetic electron bombardments. Ionization, formation of plasmas, and arcing effects due to these gas phases with the electron beam (e-beam) will be detrimental to the emitter tips and phosphor dots. Therefore, TFPs are believed to be the only solution to solve these problems. However, the relatively low efficiency of the TFPs have been kept them behind the powder phosphors in FEDs so far. The relatively low efficiency of the TFPs compared to powder phosphors, can be significantly enhanced by tailoring the surface roughness of the TFPs using various methodologies including variation in processing conditions [1-3], modifying TFP=s surface [4,5], and addition of a buffer layer between TFP and substrate [6,7]. It has been experimentally shown that the light trapping due to inte
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